Field of the Disclosure
Embodiments of the present disclosure generally relate to data storage and computer memory systems, and more particularly, to a spin-orbit torque magnetoresistive random access memory (SOT-MRAM) chip architecture.
Description of the Related Art
The heart of a computer is a magnetic recording device which typically may include a rotating magnetic media or a solid state media device. A number of different memory technologies exist today for storing information for use in a computing system. These different memory technologies may, in general, be split into two major categories: volatile memory and non-volatile memory. Volatile memory may generally refer to types of computer memory that require power to retain stored data. Non-volatile memory, on the other hand, may generally refer to types of computer memory that do not require power in order to retain stored data. Examples of volatile memory may include certain types of random access memory (RAM), such as dynamic RAM (DRAM) and static RAM (SRAM). Examples of non-volatile memory may include read-only memory (ROM), magnetoresistive RAM (MRAM), and flash memory, such as NOR and NAND flash, etc.
In recent years there has been a demand for higher density devices, which maintain a relatively low cost per bit, for use in high capacity storage and memory applications. Today the memory technologies that generally dominate the computing industry are DRAM and NAND flash; however these memory technologies may not be able to address the current and future capacity demands of next generation computing systems.
Recently, a number of emerging technologies have drawn increasing attention as potential contenders for next generation memory. One such memory technology is magnetoresistive random access memory (MRAM). MRAM offers fast access time, nearly infinite read/write endurance, radiation hardness, and high storage density. Unlike conventional RAM chip technologies, MRAM data is not stored as an electric charge, but instead stores data bits using the magnetic polarization state of magnetic elements. The elements are formed from two magnetically polarized layers, each of which can maintain a magnetic polarization field, separated by a thin insulating layer, which together form a magnetic tunnel junction (MTJ) structure. MRAM cells including MTJ memory elements can be designed for in-plane or perpendicular magnetization of the MTJ layer structure with respect to the film surface. One of the two layers (referred to as a fixed or reference layer) has its magnetization fixed and set to a particular polarity, for example by coupling the layer to an antiferromagnet; the polarization of the second layer (referred to as a free layer) is free to rotate under the influence of an external writing mechanism such as a strong magnetic field or a spin polarized electric current (which is used in a form of MRAM know as spin-torque transfer or STT-MRAM).
However, the MTJ memory elements in STT-MRAM devices suffer from wear-effects due to driving a sufficient amount of current for switching through the MTJ, including through the barrier layer. Typically, a large amount of current is required for switching the state of the cell. Over time, the barrier layer breaks down due to the large amount of current, rendering the MTJ useless.
Therefore, there is a need in the art for an improved MRAM device.